Profile plates for burner

ABSTRACT

A flame control device for a cylindrical furnace having a Tshaped gas burner unit and a fan-driven supply of air, the device comprising a pair of plates blocking the air supply to the burner except for a uniform area immediately adjacent the perimeter of the gas burner, whereby to ensure an adequate supply of air at the burner for complete combustion of the gas.

United States Patent Alms et al.

[ 51 May 2,1972

[54] PROFILE PLATES FOR BURNER [72] Inventors: Erhard E. Alms, Barrington; James E.

Mitchell, Cary, both of I11.

[73] Assignee: AFE Industries, Inc., Lake Zurich, Ill. by

said Mitchell [22] Filed: May 4, 1970 [21] Appl. No; 34,487

[52] U.S.Cl. ..431/351, 263/19A [51] Int. Cl i 1 "F23d 15/00 [58] Field ofSearch ..263/19 A; 431/351 [56] References Cited UNITED STATES PATENTS 3,044,754 7/1962 Skerkoske et al ..263/19 A 3,401,920 9/1968 Berkhoudt et al. ..263/l9 A 3,064,720 1 l/1962 Keating et al. ..263/1 9 A 3,386,715 6/1968 Alms ..263/l9 A Primary ExaminerCarroll B. Dority, Jr. Attorney--Charles F. Voytech 1 5 1 ABSTRACT A flame control device for a cylindrical furnace having a T- shaped gas burner unit and a fan-driven supply of air, the device comprising a pair of plates blocking the air supply to the burner except for a uniform area immediately adjacent the perimeter of the gas burner, whereby to ensure an adequate supply of air at the burner for complete combustion of the gas.

3 Claims, 4 Drawing Figures FIG, 1 2+ Erhard 5 Aims James 5. Mitchell PATENTEDMAY 2 I972 SHEET 2 OF 2 m Ill PROFILE PLATES FOR BURNER This invention relates to high capacity gas burners such as are used for grain dryers, and particularly to means for controlling the flow of air around such burners.

In grain dryers of the type shown in US. Pat. No. 3,056,214 to Arthur Andersen Jr., granted Oct. 2, 1962, grain is dried by forcing heated air through the perforated walls of a columnar bin containing the grain. The columnar bin is of generally oval shape having inner and outer walls, the inner wall defining a plenum chamber into which the heated air is blown by one or more fans. The air is heated by a high-capacity burner, preferably one which uses gas as a fuel. Sufficient quantities of air must be supplied to the burner not only to ensure complete combustion of the fuel, but also to bring the temperature of the products of combustion down to a level which will not injure the grain to be dried. The air therefore is drawn from the atmosphere outside the dryer by the fan or fans and blown past the gas burner where some is used in the combustion of the gas and the balance is mixed with the products of combustion and blown into the plenum chamber at a lower tem perature.

The fans used in the aforementioned Andersen dryer are of the radial propeller type one of the characteristics of which is to give the air a helical movement over the burner. The burner chamber, or furnace, is cylindrical, and the propeller type fans impart a radial outward movement to the air passing over the burner which produces a concentration of moving air at the cylindrical wall of the furnace and a lesser amount of air in the central regions of the furnace where the gas burner is located. The net result is that combustion at the burner is not complete, and the mixing of air and products of combustion is likewise not thorough so that a long flame is produced in the plenum chamber which makes for uneven drying of the grain and also creates the possibility that the grain will be scorched. To eliminate the long flame, a special mixing chamber must be added in the plenum chamber in which combustion may be completed.

In U. S. Pat. No. 3,386,715, granted June 4, 1968 to E. E. Alms, one solution to the foregoing problem is disclosed. This solution involves placing the fan between the burner and the plenum chamber so that air drawn over the burner travels substantially in straight lines instead of being concentrated at the perimeter of the furnace. The air is further diverted to travel closer to the burner rather than along the walls of the furnace chamber. The fan in said Alms patent, however, is a centrifugal fan utilizing rectangular inlet and outlet chambers, and hence the problem of the helical movement of the air does-not exist. Furthermore, it is not expedient in short dryers, i.e., dryers with short plenum chambers, to use centrifugal fans, nor is it expedient to place the fan between the burner and plenum chamber. Such short dryers are usually intended for use where the quantities of grain to be dried are not very great and the cost of the dryer is to be kept low to justify its use with such smaller quantities of grain.

The principal object of this invention is to provide a high capacity burner for a grain dryer or the like wherein means are provided for more completely burning the fuel used in said burner before said fuel enters the plenum chamber of the dryer.

As a more specific object, this invention has within its purview the provision of a simple means for controlling the flow of air from a propeller-type fan over a gas burner to improve the combustion of the gas at the burner.

A further specific object of this invention is to provide a pair of overlapping plates at the outlet of a gas burner, said plates defining an opening which is contoured to match the contour of the burner, but of larger size to leave a substantially uniform opening around the periphery of the burner through which air from a centrifugal fan may pass into the combustion chamber.

These and other objects of this invention will become apparent from the following detailed description of a preferred embodiment thereof when taken together with the accompanying drawings in which:

FIG. 1 is a schematic side elevation in cross-section of a grain dryer which incorporates the air control means of this invention;

FIG. 2 is an end elevational view in section of the dryer of FIG. 1, the section being taken along line 2-2 of FIG. 1;

FIG. 3 is an enlarged end elevational view in section of the furnace portion of the dryer of FIG. 1, the section being taken along line 3-3 of FIG. 1; and

FIG. 4 is a fragmentary side elevational view in section of the furnace portion of FIG. 3 taken along line 4-4 of FIG. 3.

Referring now to FIGS. 1 and 2, there is shown a typical dryer 10 to which this invention is particularly applicable. The dryer is shown schematically and is comprised of an outer perforated wall 11 and an inner perforated wall 12 substantially equidistantly spaced from the outer perforated wall 11. Grain to be dried, such as corn, is moved into the space 13 between the walls 1 1 and 12 by an input auger 14 disposed near the top of outer wall 11, said input auger 14 receiving the grain from a chute 15. The dried grain is removed from the space 13 by an output auger 16 located near the bottom of outer wall 11. It may be observed that the space 13 between walls 11 and 12 constitutes a pair of columnar drying bins which meet at the top and bottom of the dryer and which are simultaneously filled by the auger 14 or emptied by the auger 16.

Inner wall 12 defines with the forward end wall 17 and the rear end wall 18 a plenum chamber into which the drying medium, namely, hot gases, are introduced under a pressure which is slightly above atmospheric, so that the gases are forced through the perforated wall 12 into and through the grain in the space 13 and then into the atmosphere through the perforated outer wall 11. The hot gases are produced, in the illustrated form of this invention, by a pair of substantially identical furnaces 19 and 20 located one above the other in the forward end wall 17.

The furnaces 19 and 20 are cylindrical in radial cross-section and are comprised of a burner 21, preferably of the gas type, disposed substantially at forward wall 17, a fan 22 of the radial propeller blade type driven by an electric motor 23, and a combustion chamber 24, the latter extending substantially to the middle of the dryer. The fan 22 is located at the input end of the furnace and draws external air into the furnace past the burner 21 to supply it with the necessary oxygen for combustion and also to mix the products of combustion with outside air to bring the temperature in the furnace down to a safe level for drying the grain.

To avoid heating the upper part of combustion chamber 24 excessively, a shield 25 (FIGS. 3 and 4) of sheet metal or the like is provided, said shield having a cylindrical contour and being substantially evenly spaced from the outer wall 26 of the furnace l9. Said shield 25 terminates in outwardly extending flanges 27, 28 which abut against outer wall 26 and serve as spacers for the shield 25. Air from fan 22 is blown into the space 29 between shield 25 and outer wall 26 and serves to cool said outer wall 26.

Burner 21 may have various shapes, but in the form illustrated it is T-shaped in profile and is formed with a T -shaped input pipe or casting 30, which is provided with a series of small openings 31 facing combustion chamber 24 through which the fuel gas passes into the combustion chamber. AT- shaped perforated metal shield 32 is secured to pipe or casting 30, said shield permitting sufficient air from the fan 22 to pass through the openings 33 therein to promote combustion of the fuel gas without extinguishing the flame. As shown in FIG. 4, the shield 32 is outwardly flared to accomodate the expanding products of combustion.

It is characteristic of propeller-type fans that they impart a helical and radial movement to the air moved thereby as well as a predominantly axial movement. Since the furnace has a cylindrical contour and the burner has a T-shaped profile, a considerable portion of the air moved by the fan 22 will be located near the outer wall 26 of the furnace. The gas issuing from burner 21, therefore, may not receive enough air to burn completely in the combustion chamber 24, so that a long flame is produced extending well out of combustion chamber 24. This hot flame cannot be permitted to enter the space 13 occupied by the grain, partly because the temperature is too high to be safe and partly because uneven heating of the grain along the plenum chamber ensues which produces uneven drying of the grain.

One method proposed to eliminate the efiects of a long flame is disclosed in US. Pat. No. 3,l8l,740 to A. Andersen Jr., granted May 4, 1965. This method comprises forming a cylindrical mixing chamber at rear end wall 18 into which the flame and air are blown and wherein they are thoroughly mixed before issuing outwardly in a reverse direction into the plenum chamber. This method, however, involves the additional cost of forming a mixing chamber and eliminates the effect, rather than the cause, of the problem.

According to this invention, improved combustion at the burner 21 is achieved by compelling the air from fan 22 to flow through and around the burner 21, and by blocking the normal movement of the air near the outer wall 26 of the furnace. This is done by providing an upper plate 34 and a lower plate 35, both of which extend radially into the air stream from fan 22. Said plates are preferably made of sheet metal and have outer contours which match the inner contour of shield 25 and wall 26, including flanges 27 and 28, and inner contours which follow the profile of burner 21 butare substantially equidistantly spaced from said burner 21 to leave a space 36 immediately adjacent the burner through which air from fan 22 may pass.

Thus, upper plate 34 has a circular outer edge 37 bearing against shield 25, andan inner edge 38 which parallels the upper and side edges 39 and 40 and 41 of burner 21. Similarly, lower plate 35 has an outer edge 42 which is circular and abuts against the outer wall 26 and terminates in horizontal edges 43 and 44, which substantially abut against flanges 27 and 28, respectively, on shield 25. Lower plate 35 has an inner edge 45 which parallels the side edges 40 and 41 of the burner and also the bottom edge 46 thereof, edge 45 being rounded at 47 and 48 as a compromise to following exactly the contour of the burner which, because of the inside comer, would not provide sufficient air for the flames adjacent the edges defining such corners.

Plate 34 is'secured to shield 25 by an angle bracket 49, the latter being secured to shield 25 by any appropriate means such as a self-tapping screw. It is secured to plate 34 by a suitable threaded fastener such as a machine screw and nut. Similarly, plate 35 is secured to outer wall 26 of the furnace by a substantially identical angle bracket 50 and appropriate threaded fastener. On the sides, it may be noted that plates 34 and 35 overlap, and at these overlapping regions, the plates are secured together and to a substantially identical bracket 51 to that of bracket 49 which, in turn, is secured to the outer wall 26 by self-tapping screws.

Thus, plates 34 and 35 provide an opening around burner 21 which has a profile matching that of the burner but which essentially provides substantially equal amounts of air around the entire periphery of the burner, thus ensuring both an adequate supply of air for complete combustion of the fuel gas and a thorough mixing of the products of combustion and outside air to bring the temperature of the air in the plenum chamber to the optimum for rapid and safe drying of the grain in the columnar bin 13. The construction of the plates is extremely simple, despite the fact that an allowance must be made for shield 25 in the shape of the upper plate 34, the conformance to the shield being accomplished without resorting to cutting out a portion of the periphery of a plate.

Inasmuch as threaded fasteners, such as nuts and bolts, are used at the plates 34 and 35, the openings through which they pass may be made somewhat larger than necessary to allow for the adjustment of the plates 34 and 35 relative to the brackets, thereby to insure a close fit between the plates and shield 25 and outer wall 26.

With furnace 24 provided with plates 34 and 35 to direct the air toward the burner, greater quantities of the gaseous fuel can be burned per unit time at the burner and therefore a greater quantity of drying medium can be supplied to the plenum chamber per unit time to insure the most rapid drying of the grain without at the same time scorching or otherwise damaging the grain and without creating hot spots or uneven drying in the columnar bin 13.

We claim:

1. In combination a tubular furnace having an outer wall of predetermined cross-sectional contour, an inner wall spaced from and extending within a portion of the upper part of said furnace and terminating in flanges extending outwardly into contact with said outer wall, a gas burner in said furnace, said gas burner havinga contour different from said cross-sectional contour, means creating a stream of air through said furnace and through the space between the inner and outer walls, and means in the furnace interposed in said air stream and extending from said walls radially inwardly toward the gas burner, said last-mentioned means defining an opening around the gas burner for providing substantially equal flow of air around said gas burner, said last-mentioned means comprising further a pair of overlapping plates disposed within said furnace and havinga combined external contour which is substantially the same as the inner contour of the inner wall and the outer wall not covered by the inner wall, and unitary means securing the overlapping plates together and to the outer wall.

2. In combination a tubular furnace having an outer wall of predetermined cross-sectional contour, an inner wall spaced from and extending within a portion of the upper part of said furnace and terminating in flanges extending outwardly into contact with said outer wall, a gas burner in said furnace, said gas burner having a contour different from said cross-sectional contour, means creating a stream of air through said furnace and through the space between the inner and outer walls, and means in the furnace interposed in said air stream and extending from said walls radially inwardly toward the gas burner,

said last-mentioned means defining an opening around the gas burner for providing substantially equal flow of air around said gas burner, said last-mentioned means comprising an upper plate and a lower plate, said upper and lower plates overlapping at their adjacent edges, and means securing said overlapping edges together and to said furnace, said upper plate contacting the inner wall and having the contour thereof and said lower plate contacting the outer wall and having the contour thereof.

3. In combination a tubular furnace having an outer wall of predetermined cross-sectional contour, an inner wall spaced from and extending within a portion of the upper part of said furnace and terminating in flanges extending outwardly into contact with said outer wall, a gas burner in said furnace, said gas burner having a contour different from said cross-sectional contour, means creating a stream of air through said furnace and through the space between the inner and outer walls, and means in the furnace interposed in said air stream and extending from said walls radially inwardly toward the gas burner, said last-mentioned means defining an opening around the gas burner for providing substantially equal flow of air around said gas burner, said furnace having a substantially circular crosssectional contour, said means in the furnace interposed in the air stream comprising an upper plate and a lower plate, said upper and lower plates having overlapping adjacent edges, said upper plate having a periphery in contact with the inner wall, said lower plate having a periphery in contact with the outer wall and with the flanges on the inner wall, means securing the overlapping edges together and to said furnace, means securing the upper plate to the inner wall and means securing the lower plate to the outer wall. 

1. In combination a tubular furnace having an outer wall of predetermined cross-sectional contour, an inner wall spaced from and extending within a portion of the upper part of said furnace and terminating in flanges extending outwardly into contact with said outer wall, a gas burner in said furnace, said gas burner having a contour different from said cross-sectional contour, means creating a stream of air through said furnace and through the space between the inner and outer walls, and means in the furnace interposed in said air stream and extending from said walls radially inwardly toward the gas burner, said lastmentioned means defining an opening around the gas burner for providing substantially equal flow of air around said gas burner, said last-mentioned means comprising further a pair of overlapping plates disposed within said furnace and having a combined external contour which is substantially the same as the inner contour of the inner wall and the outer wall not covered by the inner wall, and unitary means securing the overlapping plates together and to the outer wall.
 2. In combination a tubular furnace having an outer wall of predetermined cross-sectional contour, an inner wall spaced from and extending within a portion of the upper part of said furnace and terminating in flanges extending outwardly into contact with said outer wall, a gas burner in said furnace, said gas burner having a contour different from said cross-sectional contour, means creating a stream of air through said furnace and through the space between the inner and outer walls, and means in the furnace interposed in said air stream and extending from said walls radially inwardly toward the gas burner, said last-mentioned means defining an opening around the gas burner for providing substantially equal flow of air around said gas burner, said last-mentioned means comprising an upper plate and a lower plate, said upper and lower plates overlapping at their adjacent edges, and means seCuring said overlapping edges together and to said furnace, said upper plate contacting the inner wall and having the contour thereof and said lower plate contacting the outer wall and having the contour thereof.
 3. In combination a tubular furnace having an outer wall of predetermined cross-sectional contour, an inner wall spaced from and extending within a portion of the upper part of said furnace and terminating in flanges extending outwardly into contact with said outer wall, a gas burner in said furnace, said gas burner having a contour different from said cross-sectional contour, means creating a stream of air through said furnace and through the space between the inner and outer walls, and means in the furnace interposed in said air stream and extending from said walls radially inwardly toward the gas burner, said last-mentioned means defining an opening around the gas burner for providing substantially equal flow of air around said gas burner, said furnace having a substantially circular cross-sectional contour, said means in the furnace interposed in the air stream comprising an upper plate and a lower plate, said upper and lower plates having overlapping adjacent edges, said upper plate having a periphery in contact with the inner wall, said lower plate having a periphery in contact with the outer wall and with the flanges on the inner wall, means securing the overlapping edges together and to said furnace, means securing the upper plate to the inner wall and means securing the lower plate to the outer wall. 